Second Trimester Twin Pregnancy Complications

The Science:

Fundal height is a measurement usually taken at each obstetric visit that runs from the top of the pubic bone (symphysis pubis) to the top of the uterus. It gives a rough idea as to how the pregnancy is going, running on the assumption that if the size of the uterus is growing, the baby is probably growing too.

It is normally measured in centimeters, because of a bit of biological luck that means the normal height of the fundus in cm equals the weeks of gestation (plus or minus a couple of cm) from about 20 weeks onwards.

Of course, in a multiple pregnancy where there is more than one baby in the uterus this measurement is less helpful for two reasons:

Firstly, you will inevitably measure ahead- there’s twice as much baby in there! Secondly, one baby can be growing well and one not so well, and the tape measure will still show growth. It can’t differentiate. This is the reason that multiple pregnancies often have monthly (sometimes more often depending on the type of twin pregnancy) growth scans to check on each baby individually, especially in the third trimester even if all is going well.

Other things that may happen in the second trimester, depending on your pregnancy and your caregiver:
More frequent visits.

Checks of your cervical length. This can be either manual (by vaginal examination) or with ultrasound (a more accurate method, especially if with a transvaginal approach). Since approximately half of twins will be premature, and it is hard to predict who will deliver prematurely and who is more likely to go to term, much effort has gone into finding ways to identify those at greater risk. Cervical length is one method, but it is not absolute. Having a shorter cervix to start with, early or rapid shortening of the cervix is a known risk factor for preterm delivery, but doesn’t mean it is inevitable. However, checking this can help identify women who are at increased risk of having their twins prematurely and allow closer monitoring.

Ultrasounds. Apart from the scans related to looking for abnormalities in your babies, commonly performed at 12 and 18-20 weeks of pregnancy (if you choose to screen for Down Syndrome and other conditions), you may have additional growth scans in the second trimester, especially if you have mono-chorionic twins as there are special risks with mo/di and mo/mo twins. Whatever type of twin pregnancy you have, by the third trimester you are likely to be having at least monthly growth scans. You will likely be lucky enough to see your babies on ultrasound many times before they’re born, often down to the shape of the nose, hair and thumb sucking.

If you have monoamniotic twins (mo/mo, or MCMA), you may be admitted to hospital later in the second trimester for closer monitoring of the babies.

The Science:

Treating Early Contractions

Premature labor comes in two major varieties, threatened and actual. The difference between the two is that actual premature labor is defined as uterine contractions causing cervical effacement and dilation. Threatened premature labor implies contractions without cervical change.

Medications can be given to help halt early contractions, and are especially useful in that they may allow a woman who is at risk of delivering very prematurely to be transported to a hospital with a high-level NICU and allow sufficient time for steroids to be given to help mature the babies’ lungs. There are several options, and several medications may be trialed to find the most effective for a given situation:

Nifedipine (also known as Procardia). This medication has the advantages of being available as a tablet and not requiring injections or a IV. It is a newer medication in the treatment of early contractions, and there is some evidence it may be better tolerated by the mother and associated with slightly better outcomes for the baby. The more common side effects are low blood pressure (it is more commonly used as a treatment for high blood pressure) and swelling of the ankles.

Terbutaline. This drug requires injection. It may make you feel a bit shaky and your heart may feel as if it is racing (palpitations).

Indomethacin. This is a type of drug known as a non steroidal anti inflammatory (NSAID). It is usually only used in the short term because of side effects on the babies if used for longer periods.

GTN. An angina medication in its more common use, GTN will occasionally be trialled. The major side effects are low blood pressure and headaches.

Magnesium Sulphate. This medication requires an IV infusion, and is used in hospital, often when other drugs are not effective.

Progesterone. There is research showing that in women with singleton pregnancies who have had a premature birth previously, progesterone will reduce the risk of this happening again (recurrence). Evidence is now coming out that progesterone may be useful in multiple pregnancies, too.

The Science:

Prematurity and Twins - A Bit More...

Term is normally considered to be 40 weeks of completed pregnancy with a range of 37-42 weeks allowed as normal, so by definition less than 37 weeks is premature, and over 42 is postmature. The reason that attention is paid to these dates is that mortality (death) and morbidity (illness) are higher the further on departs from the normal gestation length . In twins, 38 weeks is considered full term.

Even if term, twins are often smaller than single babies born at the same gestation as the uterus may not be able to supply two growing babies completely. This tendency to lower birth weight may also compound the effect of prematurity, as larger babies at a given gestation tend to do better than those of smaller birth weight.

Premature birth is taken quite seriously, because despite significant technological advances in the care of premature infants, there is still a significant rate of complications in babies born very premature both in the short and longer terms. Prematurity is also often a significant health expenditure in many countries.

The major trigger of prematurity in multiples is uterine ovredistension. The more babies, the more likely they are to be premature, and the earlier they will be born on average.

Around half of all twins will be premature, the average birth being at 36 weeks gestation. Around ten percent of twins will be born sooner than 32 weeks, some of which will be born very premature (before 28 weeks).

Prematurity is commonly divided up into mildly premature (less than 36 but more than 32 weeks), moderately premature (32-28 weeks) and very premature (less than 28 weeks). Extremely premature infants born in the weeks of viability (24-26 weeks) do have a high mortality rate, very sadly.

The earlier a baby is born, the greater risk of complications and the longer they are likely to need to spend in hospital. Broadly speaking, minorly premature infants may have some difficulty regulating their body temperature and blood sugars initially due to small size and are likely to need tube feeding for some of their nutrition until they grow bigger and stronger. They may occasionally have some trouble with breathing, but usually will only require CPAP (a non-invasive breathing support).

More moderately premature infants are likely to spend time in a humidi-crib, require tube feeding for longer and may need to spend some time on a ventilator to help their breathing, especially if there has not been time for steroids to be given to help mature the lungs before birth.

Very premature infants will need extensive help to keep warm, hydrated, fed and breathe and are likely to spend a long period of time in hospital.

Although most twins are born at or near term, and I personally find it hard to talk about the scary things that can happen when babies are born very early, I think it is also important to be honest and not gloss over it excessively. Babies that do come very early have risks of serious health complications including bleeding into the brain, severe infection and difficulty with their breathing, even with the aid of breathing machines. Some do pass away because of these and other complications. If they survive, they are at increased risk of long term disability. If you are in the situation where your twins are born very early, it is likely to be a very scary and emotionally intense time. Please seek support.